Consolidated Statements Of Income And Earnings Reinvested In The Business (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
INCOME
Operating Revenues	$ 1,626,853	$ 1,778,842	$ 1,760,503
Operating Expenses
Purchased Gas	415,589	628,732	658,432
Operation and Maintenance	401,397	400,519	394,569
Property, Franchise and Other Taxes	90,288	81,902	75,852
Depreciation, Depletion and Amortization	271,530	226,527	191,199
Total Operating Expenses	1,178,804	1,337,680	1,320,052
Depreciation Depletion And Amortization Excluding Discontinued Operations	271,530	226,527	191,199
Operating Income	448,049	441,162	440,451
Other Income (Expense):
Gain on Sale of Unconsolidated Subsidiaries	0	50,879	0
Other Income	5,133	5,947	6,126
Interest Income	3,689	2,916	3,729
Interest Expense on Long-Term Debt	(82,002)	(73,567)	(87,190)
Other Interest Expense	(4,238)	(4,554)	(6,756)
Income from Continuing Operations Before Income Taxes	370,631	422,783	356,360
Income Tax Expense	150,554	164,381	137,227
Income from Continuing Operations	220,077	258,402	219,133
Discontinued Operations:
Income from Operations, Net of Tax	0	0	470
Gain on Disposal, Net of Tax	0	0	6,310
Income from Discontinued Operations, Net of Tax	0	0	6,780
Net Income Available for Common Stock	220,077	258,402	225,913
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Year	1,206,022	1,063,262	948,293
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	1,426,099	1,321,664	1,174,206
Dividends on Common Stock	(119,815)	(115,642)	(110,944)
Balance at End of Year	$ 1,306,284	$ 1,206,022	$ 1,063,262
Earnings Per Common Share, Basic:
Income from Continuing Operations	$ 2.65	$ 3.13	$ 2.70
Income from Discontinued Operations	$ 0.00	$ 0.00	$ 0.08
Net Income Available for Common Stock	$ 2.65	$ 3.13	$ 2.78
Diluted:
Income from Continuing Operations	$ 2.63	$ 3.09	$ 2.65
Income from Discontinued Operations	$ 0.00	$ 0.00	$ 0.08
Net Income Available for Common Stock	$ 2.63	$ 3.09	$ 2.73
Weighted Average Common Shares Outstanding:
Used in Basic Calculation	83,127,844	82,514,015	81,380,434
Used in Diluted Calculation	83,739,771	83,670,802	82,660,598